1. Field of the Invention
The present invention relates to a liquid crystal driving device.
2. Description of the Related Art
As a liquid crystal driving device that drives a liquid crystal panel including a switching element such as TFT (Thin Film Transistor) corresponding to each of a plurality of pixels disposed in a matrix form, there is generally known a liquid crystal driving device including: a scanning line driving circuit that supplies row by row a signal for performing switching control of the switching element through a scanning line connected in parallel with the gates of a plurality of switching elements of the same row; and a data line driving circuit that supplies column by column a signal corresponding to the tone of each pixel through a data line connected in parallel with sources of a plurality of switching elements of the same column. As the scanning line driving circuit, there is generally known a scanning line driving circuit including for every scanning line a level shift circuit that amplifies a binary signal of a comparatively low voltage input from a microcomputer etc., which control the scanning line driving circuit, into a binary signal of a higher voltage for performing switching control of the switching element.
In FIG. 11 of Japanese Patent Application Laid-Open Publication No. 2005-321457, as the level shift circuit used for the scanning line driving circuit, there is disclosed an example of a configuration where a High level amplifying unit that amplifies a binary signal having potentials of VD and VS (<VD) firstly into a binary signal having potentials of VH (>VD) and VS, and a Low level amplifying unit that amplifies it secondly into a binary signal having potentials of VH and VL (<VS), are connected in series, for example. Furthermore, in FIG. 2 to FIG. 4 of Japanese Patent Application Laid-Open Publication No. 2005-321457, there is disclosed an example of a configuration where a first level shifter that amplifies a binary signal having potentials of VD and VS into a binary signal having potentials of VD and VL, and a second level shifter that amplifies it to a binary signal having potentials of VH and VS, are connected in parallel, for example.
Thus, even when it is difficult to amplify from a binary signal of a comparatively low voltage directly to a binary signal of a higher voltage, a binary signal for performing switching control of the switching element through the scanning line can be supplied by employing the above series connection configuration or parallel connection configuration.
However, the above series connection configuration or parallel connection configuration have a problem that a circuit size becomes larger, as compared with the case where a binary signal input to the level shift circuit can be amplified directly to a binary signal to be output. In particular, when the microcomputer, which controls the scanning line driving circuit etc., is driven by low voltage, there is increased the case where the difference becomes large in voltage level between a binary signal input to the scanning line driving circuit from the microcomputer and a binary signal output by the scanning line driving circuit through a scanning line, and therefore, a binary signal cannot be amplified directly. Furthermore, in the scanning line driving circuit including many scanning line outputs, the circuit size of the level shift circuit provided for every scanning line has an influence, the scale of which corresponds to the number of scanning lines, on the circuit size of the whole scanning line driving circuit.
Therefore, even when it is difficult to amplify a binary signal of a comparatively low voltage directly to become a binary signal of a higher voltage, it is preferable to realize a level shift circuit with a comparatively small-scale configuration.